A. Field of the Invention
The field of the present invention relates generally to systems for transporting surface waters away from roads, highways and other surface areas. More particularly, the present invention relates to overside drain systems that are manufactured in premolded sections which are configured to be installed in place to facilitate a relatively consistent and cost effective roadside or slope drainage system. Even more particularly, the present invention relates to such drain systems that are made of materials which provide improved drainage installation, performance and life, particularly recycled materials such as crumb rubber.
B. Background
As is well known in the road construction and maintenance industry, most roads, highways and various other surface areas are constructed using paving machines that are adapted to put down extruded curbs alongside the roadway or surface. Overside drains, which are also known as slope drains, are openings that are installed along the roads, highways and other surface areas at the edges thereof to remove surface waters from the surface area in a manner that protects nearby slopes from drainage erosion. The typical overside drain consists of various combinations of pipes, flumes, lined ditches and the like that are placed at various intervals along the length of the roadway. The spacing, placement and configuration of overside drains depends on various factors, including the configuration of the ground, the highway profile, the anticipated quantity of flow and the limitations of flooding. These factors are generally considered by the engineers and respective governmental agencies during the design of the roadway. A typical spacing for overside drains is every 100 to 150 meters.
The most common material utilized for overside drains, as well as the curbs themselves, is asphalt concrete, which consists of asphalt and mineral aggregate mixed together. When used for paving roads, highways and parking lots, the asphalt concrete is laid down in a mat and then compacted. When used for overside drains, however, the asphalt material is placed in position by hand and then troweled into the desired shape. There are three standard types of overside drains that are commonly utilized and adopted by governmental agencies (such as the California Department of Transportation or Caltrans). These standard types are commonly known as pipe drains, flume drains and paved spillways. Pipe drains typically use metal or plastic pipe to convey drainage down the side slope. This type of drain is generally used where the side slope is at a slope ratio of one to four or steeper. Most commonly, the pipe is anchored to the ground with metal stakes or the like and the mouth or inlet pipe is set into place with ground and/or asphalt around the mouth/inlet being graded to accommodate an entrance taper. The entrance taper, also known as the paved gutter flare, is currently made with asphalt concrete, as is the whole area around the mouth of the pipe drain. Flume drains are similar to pipe drains, having a paved gutter flare and the entrance area shaped with asphalt concrete. The primary difference is that flume drains have a generally rectangular corrugated metal section and the drains are best adapted to side slopes having a slope ration of one to two or flatter. Paved spillways also have paved gutter flares and are generally made entirely from asphalt concrete. This type of drain is best used at slope ratios of approximately one to four or flatter. As with pipe and flume drains, the asphalt area of paved spillways are currently built by hand with asphalt rakes, shovels and hand trowels. The use of hand tools and manual labor in forming the appropriate drain configuration requires the resources of trained crews in order to obtain a consistent and proper drain. Because such crews are often not available, the asphalt drains are often not the quality desired. In addition, paved spillway drains require the ground below the drain to be graded in a generally v-shaped or similar configuration to act as a mold or form for the bottom half of the drain.
As is well known in the industry, problems with overside drains are commonly associated with the asphalt concrete portion of the drain. The process of spreading and shaping the asphalt concrete into drain or spillway shapes using hand tools often results in very inconsistent and dimensionally incorrect drains due to poor or uninformed workmanship. Because the asphalt concrete is difficult to compress or compact, it is placed at the drain in a generally loose or non-compacted state. Although the top or outer surface is typically slicked off with a trowel or other tool to provide a smooth finish, the asphalt concrete generally has little or no significant compaction strength. The overtopping of a drain due to flooding or other higher flow causes erosion concerns for the drain, such as eroding of the drain base and supporting ground below the spillway. This can cause the asphalt concrete to crack and/or break apart and possibly even move from its place or rest into areas outside of the highway or roadway right of way, where it can cause contamination and clean-up problems. Growth of grass, weeds and other vegetation through the non-compacted asphalt concrete and cracks therein can hasten the breaking apart of the asphalt concrete drain. The damage to the asphalt concrete drainage systems can require frequent, repeated repair and, at some point in time, replacement of the entire drain. Naturally, the need for repair or replacement of the drain can significantly increase the overall cost of the drain during its planned operational life.
The need for more roads and highways, with their associated overside drains, is a direct result of the increase in the number of cars, trucks and other vehicles using such roads and highways. The increase in vehicles results in an increase in the number of tires which are utilized with those vehicles. The replacement of the tires on the vehicles results in an ever increasing problem of used tire disposal. Every year millions of tires are placed in disposal sites. In fact, in the year 2000 approximately 270 million tires, which is equivalent to about five billion pounds of tires, were discarded. Most of these tires end up in land disposal sites where they tend to accumulate in tire piles. These tire piles are well known to cause environmental and health hazards for residents in nearby communities. For instance, rainwater can accumulate in these tire piles, creating a favorable environment for the development of mosquitoes, which are known to transmit diseases to humans and animals. Another major problem with these tire piles is their unfortunate tendency to catch fire. Tire fires can become quite massive and result in millions of dollars in costs to fight the fires and clean up the environmental mess left behind by thousands of melting tires spreading rubber and chemicals over the ground and into ground and surface waters. In addition, while the tires are burning the fire pumps significant quantities of pollutants into the air, directly affecting the health of those unfortunate enough to be living nearby or passing through the area.
Recognizing the problems associated with the disposal of used tires, a number of federal, state and local governmental agencies have committed resources towards finding viable alternatives to merely disposing of the tires into landfills and other storage areas. While a relatively small amount of tires are burned directly for fuel, the greatest potential to reduce the disposal problems associated with used tires is in the field of recycling. As is well known, however, some of the materials used for making tires safer and longer lasting, such as the embedded steel belts, polyester and other materials, make the recycling of tires more difficult. Perhaps the greatest potential for recycling tires is with a material commonly referred to as crumb rubber. There are two basic methods of producing crumb rubber from used tires. One process involves grinding the used tires at or near ambient temperature into successively smaller particles until the desired particle size is obtained. The other process is a cryogenic process that uses liquid nitrogen or other material to freeze tire chips or rubber particles prior to grinding in an impact-type reduction unit, such as a hammer mill. In either process, the tires are generally formed into a granular material that can be used directly as it is or as in ingredient in the manufacturing other composite materials. For instance, crumb rubber is used alone as a ground covering material for playgrounds and the like. Crumb rubber is also used as a modifier in a mix with asphalt for asphalt paving materials. Crumb rubber is also used for sidewalks (i.e., www.rubbersidewalks.com), sport tracks and other surface areas.
As set forth above, the presently available systems for installing overside drains has a number of limitations with regard to the asphalt material used for the drains and the need to have experienced personnel installing and overseeing the installation of the drains. Specifically, the use of non-compacted asphalt and the use of hand tools and spreading techniques results in substantial inconsistencies with regard to the quality, cost and durability of overside drains. As a result, the drains generally do not provide the appearance or service that is expected of overside drain systems. What is needed, therefore, is an improved overside drain system for roads and like surface areas that provides improved consistency of installation and improved operational service. The preferred overside drain system will provide overside drains that are generally uniform in size, shape and consistency by substantially reducing the dependency on the present manual labor techniques of installing such drains. The preferred overside drain system will utilize materials that are significantly less susceptible to the erosion and breaking apart that is commonly associated with the present asphalt construction. Even more preferably, an improved overside drain system will utilize recycled materials, such as crumb rubber and the like.